three.js/examples/js/modifiers/EdgeSplitModifier.js

( function () {

	var EdgeSplitModifier = function () {

		var A = new THREE.Vector3();
		var B = new THREE.Vector3();
		var C = new THREE.Vector3();
		var positions, normals;
		var indexes;
		var pointToIndexMap, splitIndexes;
		let oldNormals;

		function computeNormals() {

			normals = new Float32Array( indexes.length * 3 );

			for ( var i = 0; i < indexes.length; i += 3 ) {

				var index = indexes[ i ];
				A.set( positions[ 3 * index ], positions[ 3 * index + 1 ], positions[ 3 * index + 2 ] );
				index = indexes[ i + 1 ];
				B.set( positions[ 3 * index ], positions[ 3 * index + 1 ], positions[ 3 * index + 2 ] );
				index = indexes[ i + 2 ];
				C.set( positions[ 3 * index ], positions[ 3 * index + 1 ], positions[ 3 * index + 2 ] );
				C.sub( B );
				A.sub( B );
				var normal = C.cross( A ).normalize();

				for ( var j = 0; j < 3; j ++ ) {

					normals[ 3 * ( i + j ) ] = normal.x;
					normals[ 3 * ( i + j ) + 1 ] = normal.y;
					normals[ 3 * ( i + j ) + 2 ] = normal.z;

				}

			}

		}

		function mapPositionsToIndexes() {

			pointToIndexMap = Array( positions.length / 3 );

			for ( var i = 0; i < indexes.length; i ++ ) {

				var index = indexes[ i ];

				if ( pointToIndexMap[ index ] == null ) {

					pointToIndexMap[ index ] = [];

				}

				pointToIndexMap[ index ].push( i );

			}

		}

		function edgeSplitToGroups( indexes, cutOff, firstIndex ) {

			A.set( normals[ 3 * firstIndex ], normals[ 3 * firstIndex + 1 ], normals[ 3 * firstIndex + 2 ] ).normalize();
			var result = {
				splitGroup: [],
				currentGroup: [ firstIndex ]
			};

			for ( var j of indexes ) {

				if ( j !== firstIndex ) {

					B.set( normals[ 3 * j ], normals[ 3 * j + 1 ], normals[ 3 * j + 2 ] ).normalize();

					if ( B.dot( A ) < cutOff ) {

						result.splitGroup.push( j );

					} else {

						result.currentGroup.push( j );

					}

				}

			}

			return result;

		}

		function edgeSplit( indexes, cutOff, original = null ) {

			if ( indexes.length === 0 ) return;
			var groupResults = [];

			for ( var index of indexes ) {

				groupResults.push( edgeSplitToGroups( indexes, cutOff, index ) );

			}

			var result = groupResults[ 0 ];

			for ( var groupResult of groupResults ) {

				if ( groupResult.currentGroup.length > result.currentGroup.length ) {

					result = groupResult;

				}

			}

			if ( original != null ) {

				splitIndexes.push( {
					original: original,
					indexes: result.currentGroup
				} );

			}

			if ( result.splitGroup.length ) {

				edgeSplit( result.splitGroup, cutOff, original || result.currentGroup[ 0 ] );

			}

		}

		this.modify = function ( geometry, cutOffAngle, tryKeepNormals = true ) {

			if ( geometry.isGeometry === true ) {

				console.error( 'THREE.EdgeSplitModifier no longer supports THREE.Geometry. Use THREE.BufferGeometry instead.' );
				return;

			}

			let hadNormals = false;
			oldNormals = null;

			if ( geometry.attributes.normal ) {

				hadNormals = true;
				geometry = geometry.clone();

				if ( tryKeepNormals === true && geometry.index !== null ) {

					oldNormals = geometry.attributes.normal.array;

				}

				geometry.deleteAttribute( 'normal' );

			}

			if ( geometry.index == null ) {

				if ( THREE.BufferGeometryUtils === undefined ) {

					throw 'THREE.EdgeSplitModifier relies on THREE.BufferGeometryUtils';

				}

				geometry = THREE.BufferGeometryUtils.mergeVertices( geometry );

			}

			indexes = geometry.index.array;
			positions = geometry.getAttribute( 'position' ).array;
			computeNormals();
			mapPositionsToIndexes();
			splitIndexes = [];

			for ( var vertexIndexes of pointToIndexMap ) {

				edgeSplit( vertexIndexes, Math.cos( cutOffAngle ) - 0.001 );

			}

			const newAttributes = {};

			for ( const name of Object.keys( geometry.attributes ) ) {

				const oldAttribute = geometry.attributes[ name ];
				const newArray = new oldAttribute.array.constructor( ( indexes.length + splitIndexes.length ) * oldAttribute.itemSize );
				newArray.set( oldAttribute.array );
				newAttributes[ name ] = new THREE.BufferAttribute( newArray, oldAttribute.itemSize, oldAttribute.normalized );

			}

			var newIndexes = new Uint32Array( indexes.length );
			newIndexes.set( indexes );

			for ( var i = 0; i < splitIndexes.length; i ++ ) {

				var split = splitIndexes[ i ];
				var index = indexes[ split.original ];

				for ( const attribute of Object.values( newAttributes ) ) {

					for ( let j = 0; j < attribute.itemSize; j ++ ) {

						attribute.array[ ( indexes.length + i ) * attribute.itemSize + j ] = attribute.array[ index * attribute.itemSize + j ];

					}

				}

				for ( var j of split.indexes ) {

					newIndexes[ j ] = indexes.length + i;

				}

			}

			geometry = new THREE.BufferGeometry();
			geometry.setIndex( new THREE.BufferAttribute( newIndexes, 1 ) );

			for ( const name of Object.keys( newAttributes ) ) {

				geometry.setAttribute( name, newAttributes[ name ] );

			}

			if ( hadNormals ) {

				geometry.computeVertexNormals();

				if ( oldNormals !== null ) {

					const changedNormals = new Array( oldNormals.length / 3 ).fill( false );

					for ( const splitData of splitIndexes ) changedNormals[ splitData.original ] = true;

					for ( let i = 0; i < changedNormals.length; i ++ ) {

						if ( changedNormals[ i ] === false ) {

							for ( let j = 0; j < 3; j ++ ) geometry.attributes.normal.array[ 3 * i + j ] = oldNormals[ 3 * i + j ];

						}

					}

				}

			}

			return geometry;

		};

	};

	THREE.EdgeSplitModifier = EdgeSplitModifier;

} )();